1.1.3 Rhodium/Palladium Dual Catalysis

This chapter reviews the development and applications of rhodium/palladium dual catalysis in organic synthesis. Dual catalysis can be broadly classified into two types: (1) Synergistic dual catalysis, where two independent rhodium and palladium catalytic cycles operate simultaneously to activate two different starting materials with balanced kinetics to afford two catalytically activated intermediates. These activated intermediates react with each other to afford the final product. (2) Orthogonal tandem dual catalysis, where two catalytic cycles operate in a sequential manner, one after the other, to promote two or more mechanistically distinct reaction steps in a single pot to furnish the product. The first part of the chapter covers synergistic rhodium/palladium dual catalysis, detailing examples that feature a direct reaction between rhodium-activated intermediates and orthogonal, palladium-activated intermediates. The second part of the chapter describes one-pot reactions that utilize initial rhodium catalysis and sequential palladium catalysis. A single example where initial palladium catalysis is followed by subsequent rhodium catalysis is also presented.